Flexural ductility of RC elements: influences of size effects and bending-shear interaction

Under seismic loading, some structural elements are subjected to combined solicitations (bending-shear for isntance). The flexural ductility of a reinforced concrete element reduces its shear capacity. In fact, during plastic dissipation (by cracking), the transfer mechanisms of the shear force are impacted, which can lead to a brittle failure. The description of this interaction is based firstly on a good estimation of the flexural ductility. The bending behavior of reinforced concrete elements are influenced by the size effect. The objective of this work is to propose an approach for describing the flexure--shear interaction taking into account the size effect. Comparisons with experimentation show the capacity of the proposed approach to describe the above mentioned phenomena

Flexural ductility of RC elements: influences of size effects and bending-shear interaction

Under seismic loading, some structural elements are subjected to combined solicitations (bending-shear for isntance). The flexural ductility of a reinforced concrete element reduces its shear capacity. In fact, during plastic dissipation (by cracking), the transfer mechanisms of the shear force are impacted, which can lead to a brittle failure. The description of this interaction is based firstly on a good estimation of the flexural ductility. The bending behavior of reinforced concrete elements are influenced by the size effect. The objective of this work is to propose an approach for describing the flexure--shear interaction taking into account the size effect. Comparisons with experimentation show the capacity of the proposed approach to describe the above mentioned phenomena.Sous chargement sismique, certains éléments structurels subissent des sollicitations combinées (flexion et cisaillement). La ductilité flexionnelle d’un élément en béton armé réduit sa capacité de cisaillement. En effet, lors de la dissipation plastique (par fissuration par exemple), les mécanismes de transfert de l’effort tranchant sont réduits pouvant engendrer une rupture brutale par cisaillement. La description de cette interaction repose tout d’abord sur une bonne estimation de la ductilité flexionnelle. Cependant, cette dernière est-elle même affectée par plusieurs paramètres. L’effet d’échelle influe de manière directe sur le comportement flexionnel des éléments en béton armé. L’objectif de ce travail est de proposer une approche permettant de décrire l’interaction flexion-cisaillement tout en tenant compte de l’effet d’échelle dans la prédiction du comportement flexionnel. Des comparaisons avec l’expérimentation montrent la capacité de l'approche proposée à décrire les phénomènes évoqués.Under seismic loading, some structural elements are subjected to combined solicitations (bending-shear for isntance). The flexural ductility of a reinforced concrete element reduces its shear capacity. In fact, during plastic dissipation (by cracking), the transfer mechanisms of the shear force are impacted, which can lead to a brittle failure. The description of this interaction is based firstly on a good estimation of the flexural ductility. The bending behavior of reinforced concrete elements are influenced by the size effect. The objective of this work is to propose an approach for describing the flexure--shear interaction taking into account the size effect. Comparisons with experimentation show the capacity of the proposed approach to describe the above mentioned phenomena

On the use of excavated earth hemp mortars as thermal insulation materials

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Characterization of tunnel excavated earth-based mortars for rammed earth repair

The aim of this work is to study the possibility to reuse the tunnel excavated earth in order to elaborate earth-based mortar for rammed earth reparation. The tunnel excavated earth-based mortars were compared with raw earth based-mortars, largely used in practice. The cement was used as stabilizer and the hemp fibers were used to diminish the cracking due to shrinkage. The mechanical, thermal and hydric properties of mortars were characterized after 28 days. The mortars were maintained in hydrothermal chamber at controlled conditions, 20 ± 2 °C and 50 ± 5 HR. The obtained results show that the mechanical performances increase with the increase of cement by earth ratio. While, the increase of cement content affects negatively the thermal conductivity of earth-based mortars. Whereas, the thermal properties were improved with the addition of natural fiber. The excavated earth-based mortars show higher mechanical performances and good thermal properties compared to raw earth-based mortars

Recovery of excavated materials as an alternative solution to earth building materials

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Effect of Used Engine Oil Addition on the Rheological Properties of a Plastic Bag Waste–Modified 40/50 Grade Bitumen

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Granulome à cholestérine de l\'apex pétreux. Intérêt de l\'irm CHOLESTEROL Granuloma of the petrous apex. MRI contribution (Francais )

Background Cholesterol granuloma is an expansive lesion developing into air cavities of the facial bones and base of the skull. This pathology is relatively rare, usually localized at the level of the petrous bone. Its diagnosis is oriented by clinical sign and is made on magnetic resonance imaging (MRI) Objective To show the interest of MRI in the diagnosis of cholesterol granuloma. Patient This patient was 43 years-old and was complaining with a progressive right hypoacousia, a full ear sensation and a hyposensibility of the right face. An audiometry, a CT scan and a MRI in T1 and T2 weighted sequence have been achieved. Results A right perception deafness was found. CT scan showed an expansive lesion of the right petrous apex with an osteolysis of the carotid canal. MRI showed a mass located in the right petrous apex with a T1 and T2 hypersignal. The patient was operated on using an infralabyrinthine route through a retroauricular approach. A mastoïdectomy were used to operate the patient enabling the visualisation of the posterior part of the cyst and to drain it into the mastoid. Conclusion The cholesterol granuloma of petrous apex is a lesion growing slowly with progressive otoneurological signs. The diagnosis is mainly radiological using MRI which shows a lesion hyperintense in T1 and T2. Résumé Introduction Le granulome à cholestérine est une lésion expansive osseuse des cavités pneumatiques, relativement rare, localisée habituellement au niveau de l\'os temporal. Son diagnostic orienté par les signes cliniques repose sur l‚imagerie par résonance magnétique (IRM). Objectif Préciser l\'intérêt de l\'IRM dans le diagnostic positif de cette pathologie. Observation : le patient âgé de 43 ans a présenté de façon progressive une hypoacousie droite, des acouphènes, une sensation d\'oreille pleine et une hyposensibilité de l\'hémiface droite. Une audiométrie, un examen scanographique (TDM) et une IRM en séquence pondéré en T1 et T2 cérébrale ont été réalisées. Résultats L\'audiométrie a relevé une surdité de perception droite. La TDM a objectivé un processus expansif de l‚apex pétreux droit au contact du canal carotidien qui présente une lyse de la paroi postéro-latérale. L\'IRM a montré une masse occupant l\'apex pétreux droit en hypersignal T1et T2 à contours nets. Le patient a été opéré par une voie infra-labyrintique. Une mastoïdectomie a été réalisée par voie postérieure permettant de visualiser la paroi postérieure du kyste qui a été incisé afin de permettre sa vidange et un drainage large dans la mastoïde. Conclusions Le granulome à cholestérine de l\'apex pétreux est une lésion à croissance lente et à expression clinique progressive présentant une symptomatologie oto-neurologique progressive par compression. Le diagnostic est essentiellement radiologique par l\'IRM qui montre une lésion hyperintense en T1 et T2. (Af. J. of Neurological Sciences: 2003 22(2)